Atmospherically-controlled switch



Sept. 20, 1927.

J. E. BOLLING ATMOSPHERICALL-Y CONTROLLED SWITCH Filed Jan. 11. 1926 TEMPIRA TUB E I nve ntor John E. Bolling Witnesses.

By Y Attyba Patented Sept. 20, 1927.

UNITED STATES- PATENT or'rrca.

JOHN EJBOLLING, OF CHICAGO, ILLDIOIE. ABSIGROB. TO DRYING BYSTEHB, INC., CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

ATIIOBPHEKICALLY-GOFTBOLIJD -pp11catton ma January n, ma lerta'l Ho. some.

This inventioin relates to improvements in control instruments such as thermostats and the like, and more particularly to the electri:

.cal switch mechanism therefor, and is chiefly characterized by providing a counterweight for'the shifting mercury globule.

Heretofore diilieulty has been encountered in such instruments in obtaining a high dc greeot accuracy at the point at which the 1o electrical switch-is operated, on account of the resistance suddenly added to the mov able element of the device in overcoxnin the unbalanced weight 'of the mercury glo ule. I It is, therefore, an object of this invention is to improve the operation of the instrument by providing meansrior suitably balancing the globule in the various positions.

An illustrative embodiment of the invention is shown in the accompanying drawin which igure 1 is an elevation of the switch and adjacent portions of an atmospheric control instrument.

Fig. 2 is a view similar to Fig. 1', showing the switch inthe opposite position. i

Fig. 3 is a diagram of the movement of the responsive element of the instrument.

Fig. 4 is a section substantially on the line 4'-4 of Fig. 1. y

In the drawings, the glass switch bulb 1 is provided with contacts 2 and 3 at the outer end thereof. In the position shown in Fig. 1, the switch bulb is tilted to the left so that the mercury globule 4 has run over to the as outer end, and serves as a contactor between the switch points 2 and 3. The bulb is held in the clip portion 5 of the sheet metal saddle 6, by means of the bolt 7. A lug 8 is stamped out and bent downward from the bottom of the member 6 to provide a contact point for resting on the end of the movable member 9 of the instrument. At the inner end of the sheet metal member 6, the flat portion 10 is bent downwardly and terminates in a threaded portion 11 for the counterweigl'lt 12. The pivotal mounting of the switch comprises a post 14 secured in the frame 15 of the instrument, and the post 14 engages in the lugs 16, which are bent up from the tint tail portion 10.

As shown, the switch bulb 1 is mounted above the pivot 14. The switch overhangs to the leftof the pivot, and the counter-balanc is hung below the ivot so that the hori- 55 zontal movement of tie counter-balance is lop osite to the horizontal movement of the jmercurfi globule 4 as the'switch isrotated.

in s arrangement the weight of the switch bulb and the clip 6 serves to hold the contact point 8 resting on the end of the member 9, and the counter-balance 12 is to be proportioned for counter-balancin only the globule 4. \Vhen the element 9 raises in shifting the switch from the position shown in Fig. 1 to the position shown in Fig. 2, the mercury will cling somewhat to the switch points and then run to the opposite end of the bulb when the bulb angle is a few degrees above the horizontal. During the tilt ing movement the counter-weight 12is moving under the pivot 14, and in the off position, Fig. 2, the counter-balance 12 may even be sli htly to the left of the pivot. 14 when the gobule is to the right of the pivot as shown in Fig. It is to be understood that the member 9 is moved in any well-known manner, such as by a thermal expansiible bellows, a Bourdon tube, or other well-known responsive element.

-It being understood that the member 9 is moved a shoit distance up or down by changes in temperature, it is apparent that the weight of the glass bulb andthe holder 6 on the actuating rod 9 is substantially constant since the vertical line through the center of ravity of these parts does not shift materia ly with respect to the axis. But 'the' mercury globule-4 shifts from a position to the left of the axis to a position slightly to the right, Fig. 1 and Fig. 2. This of course produces a variable load on the actuating rod 9 which is found to be sutlicient to materially affect the accuracy of the instrument.

The counterbalance 12 is provided solely for the purpose of compensating for the weight of the mercury 4. By suspending the counterweight below the axis 14, the counterweight moves oppositely to the mercury. In the position shown in Fig. 1,- the mercury exerts a counterclockwise rotational movement about the axis 14. which is compensated for by the clockwise rotational move. ment exerted by the counterweight 12.

In the oil position shown in Fig. 2, the mercury is over or slightly to the right of the axis while the center of gravity ot the counterweight is below Or may be slightly to the left of the axis. In this manner the difl'erence in the-16nd,, or the resistance ap plied to operating member 9 by the changes in the position 'of the mercury globule is overcome. in a simple manner;

' For illustrating the efiect of the weight of the mercury globule,in Fig', 3 the distances on'the X misrepresent rou hl the'diil'erout tempe atures-end thel on the Y axis, ..for the curve 6', 're 'resent,the various positions-of the inovabe member 6. The

eights 9n the Y ex is for the mistanoe curve d representjthe' opposizg the movement oi-member 9. Thecurve illus-' trates the epp'roxim'ate relative resistances co "ending to the vairious temperatures resulting in-the movement curve 6, assuming that the increasein energy for moving XS substantially constant {for equal changes c rqt In instruments commonly .-used,-the-r si tgmoe is usually p gaccordingl increases at'an .even rate-as represent by the I would,

-thennb'stat.

balancing the mercury globule the resistance' d; and the slope o the movement curve b course, correspond to the slope ofythe c e 'd with even rates of increase in the power. 'Linef re resents the point at which it is desired to ave the instrument operate, which' wonld be apredetermined temperature rovid ing the instrument is a ithout means for counterwould startto increase at temper-astute It 'where the'movable-element totlift the end .of the switch bulb; The mistzmce would [increase to the high globules-is int I: where run to the opposite end of the hulb.- There,

'fore at the precise position where accuracy is desired, the movement is slowed-up, as shownv b. thecurv'e e, and the actua-llpoint of brea the electrical switch Wlll be around the m, "which is, us a result, a varicble distance from the temperature Accordingly, inithisinvention, by providing means to counter-balance the w ht'of the mercury the m v ement will not be s uddenljf increased,

and the insulting action of: the switch willbe much more accurate.

general slope of the line.

andstm'ts. to

.Although but one specificcmbodimenthas been herem shown and described it will be understood that numerous details of'the construction shown may be altered or omitted without departing from the spirit of this invention.

I claim: 7 A 1. .In combination, in an at-mosph controlled device having a moval'ny responeri cally sive member, a. pivotally mounted mercury bulb switchresting on said member and hnvmg the mercury'globulc thereof shift able with respect to the pivotal axis, and a counterweight attached to the switch and movable therewith for counterbalsncing the weight of said globule in the. extreme positions 2. In combination in an atmospherically controlled device having a movably responsive member, a. bulb switch resting on said .member 'said switch havinv a, pivot and having a. mercury contacmr g obule shiftable with respect to said pivot and an adjustable 1 counterweight for counter-balancing said globule said counterweight attached to said -axis for tilting to either side of the horizontnl position to shift said counterweight attached to saidbulb and po sitioned'on the opposite side of the axis to produce counter-rotational movements tb. the rotstionnl'movements produced by the globtile in either extreme position.

n d a ary, 1926'.

JOHN E. BOIJLING.

lobule, and r.

Chimgothis 6th day i Jsmh' 

